One-time-programmable memory devices

Abstract

A memory device is disclosed. The memory device includes a memory array comprising a plurality of memory cells. At least a first one of the memory cells, by default, permanently presents a first logic state based on a short circuit. At least a second one of the memory cells, by default, permanently presents a second logic state opposite to the first logic state based on an open circuit.

What is claimed is: 
     
         1 . A memory device, comprising:
 a memory array comprising a plurality of memory cells;   wherein at least a first one of the memory cells, by default, permanently presents a first logic state based on a short circuit; and   wherein at least a second one of the memory cells, by default, permanently presents a second logic state opposite to the first logic state based on an open circuit.   
     
     
         2 . The memory device of  claim 1 , wherein the memory cells each include an efuse memory cell. 
     
     
         3 . The memory device of  claim 2 , wherein the first memory cell includes a transistor formed along a major surface of a substrate. 
     
     
         4 . The memory device of  claim 3 , wherein the first memory cell further includes:
 a first metal track disposed over the major surface and extending along a first lateral direction;   a second metal track disposed over the major surface, extending along the first lateral direction, and spaced apart from the first metal track along a second lateral direction perpendicular to the first lateral direction;   a third metal track disposed over the first and second metal tracks, and extending along the second lateral direction;   a fourth metal track disposed over the first and second metal tracks, and extending along the second lateral direction; and   a fifth metal track disposed over the first and second metal tracks, extending along the second lateral direction, and interposed between the third and fourth metal tracks;   wherein the third and the fourth metal tracks each electrically couple the first metal track to the second metal track so as to form the short circuit; and   wherein the fifth metal track is electrically isolated from each of the first metal track and second metal track.   
     
     
         5 . The memory device of  claim 4 , wherein the third and fourth metal tracks each have a first width along the first lateral direction and the fifth metal track has a second width along the first lateral direction, and wherein the first width is substantially greater than the second width. 
     
     
         6 . The memory device of  claim 2 , wherein the second memory cell includes a transistor formed along a major surface of a substrate. 
     
     
         7 . The memory device of  claim 6 , wherein the second memory cell further includes:
 a first metal track disposed over the major surface and extending along a first lateral direction;   a second metal track disposed over the major surface, extending along the first lateral direction, and spaced apart from the first metal track along a second lateral direction perpendicular to the first lateral direction;   a third metal track disposed over the first metal track, and extending along the second lateral direction;   a fourth metal track disposed over the second metal track, and extending along the second lateral direction;   a fifth metal track disposed over the first metal track, extending along the second lateral direction, and spaced apart from the third metal track along the first lateral direction;   a sixth metal track disposed over the second metal track, extending along the second lateral direction, and spaced apart from the fourth metal track along the first lateral direction; and   a seventh metal track disposed over the first and second metal tracks, extending along the second lateral direction, and interposed between the third and fifth metal tracks and between the fourth and sixth metal tracks;   wherein the third and fifth metal tracks are each electrically coupled to the first metal track and the fourth and sixth metal tracks are each electrically coupled to the second metal track, but the third metal track is electrically isolated from the fourth metal track and the fifth metal track is electrically isolated from the sixth metal track so as to form the open circuit; and   wherein the seventh metal track is electrically isolated from each of the first metal track and second metal track.   
     
     
         8 . The memory device of  claim 7 , wherein the third to sixth metal tracks each have a first width along the first lateral direction and the seventh metal track has a second width along the first lateral direction, and wherein the first width is substantially greater than the second width. 
     
     
         9 . The memory device of  claim 1 , wherein the memory cells each include an anti-fuse memory cell. 
     
     
         10 . The memory device of  claim 9 , wherein the first memory cell includes a reading transistor and a programming transistor connected to each other in series, wherein the reading transistor has a first threshold voltage and the programming transistor has a second threshold voltage, and wherein the second threshold voltage is substantially lower than the first threshold voltage so as to form the short circuit. 
     
     
         11 . The memory device of  claim 9 , wherein the second memory cell includes a reading transistor and a programming transistor connected to each other in series, wherein the reading transistor has a first threshold voltage and the programming transistor has a second threshold voltage, and wherein the second threshold voltage is substantially higher than the first threshold voltage so as to form the open circuit. 
     
     
         12 . The memory device of  claim 1 , wherein respective positions of the first memory cell and second memory cell in the memory array are preconfigured. 
     
     
         13 . A memory device, comprising:
 a memory array comprising a plurality of one-time-programmable (OTP) memory cells;   wherein a first subset of the OTP memory cells are configured to permanently present a first logic state based on a short circuit; and   wherein a second subset of the OTP memory cells are configured to permanently present a second logic state opposite to the first logic state based on an open circuit.   
     
     
         14 . The memory device of  claim 13 , wherein the first subset of OTP memory cells each include:
 a transistor coupled to the short circuit;   a first metal track disposed over the transistor and extending along a first lateral direction;   a second metal track disposed over the transistor, extending along the first lateral direction, and spaced apart from the first metal track along a second lateral direction perpendicular to the first lateral direction;   a third metal track disposed over the first and second metal tracks, and extending along the second lateral direction;   a fourth metal track disposed over the first and second metal tracks, and extending along the second lateral direction; and   a fifth metal track disposed over the first and second metal tracks, extending along the second lateral direction, and interposed between the third and fourth metal tracks;   wherein the third and the fourth metal tracks each electrically couple the first metal track to the second metal track so as to form the short circuit; and   wherein the fifth metal track is electrically isolated from each of the first metal track and second metal track.   
     
     
         15 . The memory device of  claim 14 , wherein the third and fourth metal tracks each have a first width along the first lateral direction and the fifth metal track has a second width along the first lateral direction, and wherein the first width is substantially greater than the second width. 
     
     
         16 . The memory device of  claim 13 , wherein the second subset of OTP memory cells each include:
 a transistor coupled to the open circuit;   a first metal track disposed over the major surface and extending along a first lateral direction;   a second metal track disposed over the major surface, extending along the first lateral direction, and spaced apart from the first metal track along a second lateral direction perpendicular to the first lateral direction;   a third metal track disposed over the first metal track, and extending along the second lateral direction;   a fourth metal track disposed over the second metal track, and extending along the second lateral direction;   a fifth metal track disposed over the first metal track, extending along the second lateral direction, and spaced apart from the third metal track along the first lateral direction;   a sixth metal track disposed over the second metal track, extending along the second lateral direction, and spaced apart from the fourth metal track along the first lateral direction; and   a seventh metal track disposed over the first and second metal tracks, extending along the second lateral direction, and interposed between the third and fifth metal tracks and between the fourth and sixth metal tracks;   wherein the third and fifth metal tracks are each electrically coupled to the first metal track and the fourth and sixth metal tracks are each electrically coupled to the second metal track, but the third metal track is electrically isolated from the fourth metal track and the fifth metal track is electrically isolated from the sixth metal track so as to form the open circuit; and   wherein the seventh metal track is electrically isolated from each of the first metal track and second metal track.   
     
     
         17 . The memory device of  claim 16 , wherein the third to sixth metal tracks each have a first width along the first lateral direction and the seventh metal track has a second width along the first lateral direction, and wherein the first width is substantially greater than the second width. 
     
     
         18 . The memory device of  claim 13 , wherein respective positions of the first subset of memory cells and second subset of memory cells in the memory array and respective numbers of the first subset of memory cells and second subset of memory cells are preconfigured. 
     
     
         19 . A method, comprising:
 forming a plurality of transistors along a major surface of a substrate; and   forming a plurality of metal tracks over the plurality of transistors;   wherein a first one of the transistors, together with at least a first one of the plurality of metal tracks, collectively form a first memory cell, in which the first metal track forms a short circuit coupled to the first transistor; and   wherein a second one of the transistors, together with at least a third one and a fourth one of the plurality of metal tracks collectively form a second memory cell, in which the third and fourth metal tracks form an open circuit coupled to the second transistor.   
     
     
         20 . The method of  claim 19 , wherein the first memory cell, by default, permanently presents a first logic state based on the short circuit, and the second memory cell, by default, permanently presents a second logic state based on the open circuit.